It is known that fuel tanks have many different forms. With the fuel tank being adapted to the motor vehicle, so as to utilize the existing construction space, fuel tanks which are subdivided into a plurality of chambers are obtained.
These chambers are for the most part connected to a saddle. In fuel tanks of this type, there is the problem that, in the case of a low filling level, the fuel can no longer pass out of one chamber over the saddle into the other chamber. Since normally only one conveying unit is arranged in a fuel tank, the fuel located in another chamber cannot reach the conveying unit. In these instances, suction jet pumps are used in order to supply the fuel present in other regions of the fuel tank to the conveying unit or to convey the fuel at least into the chamber or the region in which the conveying unit is located (DE 37 32 415 A1).
Conventional suction jet pumps are arranged at the bottom of the chambers or the regions of the fuel tank out of which the fuel is to be conveyed to the conveying unit. Since the intake orifice of the suction jet pump is arranged at the bottom of the fuel tank, the suction jet pump is always located in the fuel and is therefore always ready for operation. Suction jet pumps of this type have high efficiency. The conveyance factor, that is to say the ratio of the sum jet to the propulsion jet, is at least in the region of seven. The disadvantage, here, is that, with the propellant line to the suction jet pump and the sum line from the suction jet pump, two lines are required which have to be laid and fastened in the fuel tank.
Furthermore, it is known to use sucking suction jet pumps which are arranged in the region of the conveying unit. A suction line leads from the suction jet pump into the region out of which the fuel is to be conveyed. To generate the necessary vacuum in the suction line, the suction jet pump possesses a special propulsion jet nozzle. The outlet orifice of the propulsion jet nozzle is designed as a slit. On account of the slit, the propulsion jet is fanned open after emerging from the propulsion jet nozzle. The fanned-open propulsion jet closes the mixing tube, with the result that the necessary vacuum is generated so that the fuel can be sucked in via the relatively long intake line. On account of this, it is necessary to have instead of two, as hitherto, only one line to be laid and fastened in the fuel tank. This embodiment has the disadvantage of the low conveyance factor of the sucking suction jet pump which is approximately 2. This low conveyance factor is due to the fanning open of the propulsion jet after leaving the propulsion jet nozzle.
The object on which the present invention is based, therefore, is to provide a sucking suction jet pump having an improved conveyance factor. Furthermore, the suction jet pump is to have a simple and compact construction and be easy to mount.
Other objects will become apparent upon a further reading of the following detailed description taken in conjunction with the drawings.
The object is achieved by means of the features of claim 1. Advantageous refinements are contained in the subclaims.